Preparation method of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres and application thereof

Abstract

The application relates to a preparation method of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres and application thereof, and the specific steps are as follows: ammonia is dispersed into a prepared dilute ethanol solution to obtain solution A; a dopamine solution is added into the solution A to stir to form a suspension B, and polydopamine microspheres PDA are obtained through washing, collecting and drying; a titanium source is added into the PDA dispersion to stir to form a suspension C; the suspension C is mixed with ethanol and then added into deionized water to form a suspension D, and core-shell structure titanium dioxide microspheres PDA@TiO2 are obtained through washing, collecting and drying. The PDA@TiO2 is placed in a muffle furnace to be calcined to obtain nitrogen-carbon co-doped titanium dioxide hollow microspheres. The titanium dioxide hollow microspheres prepared by the method have the characteristics of an ultrathin shell, nitrogen-carbon co-doping, porosity and rich oxygen vacancies, and the removal efficiency of flowing gaseous acetaldehyde under visible light reaches 90%.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of nanomaterial preparation, and particularly relates to a preparation method of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres and application thereof. BACKGROUND

[0002] Acetaldehyde is a volatile organic compound (VOCs), and its large-scale production in industry and extensive use in household appliances can cause increasingly serious indoor / outdoor air pollution. The large amount of acetaldehyde in the air can not only induce secondary pollutants such as PM2.5 and O3, but also stimulate human organs and even cause cancer, thereby threatening human health and ecological balance. Compared with other air pollutant purification technologies such as adsorption, condensation, membrane separation and combustion, the solar-driven photocatalytic oxidation technology has the characteristics of complete degradation and sustainable development.

[0003] At present, commonly used photocatalysts include zinc oxide, carbon nitride and metal sulfide, but the photocatalytic activity of these materials is limited by problems such as easy corrosion by light, toxic effect and high cost. Titanium dioxide has the characteristics of strong oxidizing property, high photochemical stability, non-toxicity and low cost, and is widely used in the fields of energy and environmental photocatalysis. In recent years, scientists have found that anatase titanium dioxide has many advantages compared with rutile titanium dioxide, such as a more favorable oxidation potential, a higher specific surface area and stronger photocatalytic activity.

[0004] However, the large band gap (3.2 eV) of anatase titanium dioxide brings excellent oxidation performance, but also limits its light absorption ability in the long-wave visible light. Pure anatase titanium dioxide can only absorb short-wave ultraviolet light with a wavelength of less than 400 nm, but the energy of ultraviolet light accounts for only about 5% of the total energy of sunlight. Moreover, the high recombination rate of photo-generated carriers of pure anatase titanium dioxide leads to low photocatalytic efficiency in the visible light band. Therefore, it is of great significance to design and develop anatase titanium dioxide hollow microspheres with good visible light absorption and high carrier separation efficiency.

[0005] The multiple refraction of light inside the hollow microspheres can compensate for the defects of TiO2 such as poor light absorption and high recombination rate of photo-generated carriers to a certain extent, and has broad application prospects in photocatalysis. However, there are still challenges in the hollow microspheres: 1) the types of template agents are single, and are mostly limited to silica (SiO2) and polystyrene (PS) microspheres, wherein SiO2 removal requires the use of high-risk etchants such as hydrofluoric acid, and PS synthesis has high temperature and complicated steps; 2) an ultra-thin shell is beneficial to exposing active sites to improve catalytic performance, but the mechanical stability of the too-thin shell is poor, and it is difficult to obtain a complete spherical shell.

[0006] Polydopamine (PDA) microspheres are spontaneously polymerized from dopamine monomers (DA) under alkaline conditions, which as a kind of melanin-like material has the characteristics of green environmental protection and room temperature synthesis. If PDA spheres are used as a hard template, it will have many advantages, but there are few reports. First, PDA has a polyphenol structure, containing multiple amino and hydroxyl functional groups, which can coat most materials on its surface without any modification; second, PDA contains a large amount of carbon, and the hollow structure obtained by pyrolysis of PDA template can provide a large amount of nitrogen and carbon source atmosphere. Non-metallic doping such as nitrogen and carbon is widely used to construct surface defects such as oxygen vacancies of metal oxides, which is beneficial to further improve the visible light absorption and charge separation of titanium dioxide. Therefore, PDA microspheres are expected to provide a green and multifunctional template for the construction of titanium dioxide hollow microspheres with good visible light absorption and high carrier separation efficiency. SUMMARY

[0007] The purpose of the present application is to solve the problems of weak visible light absorption and high photo-generated carrier recombination rate of anatase titanium dioxide, and to provide a preparation method of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres and its photocatalytic application. The polydopamine sphere template used in this method is green and environmentally friendly, the material preparation method is simple and safe, and the obtained titanium dioxide hollow microsphere product has an ultra-thin hollow shell and rich porosity and oxygen vacancies, and has high catalytic oxidation efficiency for flowing gaseous acetaldehyde under visible light driving, which has good application prospect.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres, comprising the following steps:

[0009] (1) 40 mL of anhydrous ethanol is dissolved in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L;

[0010] (2) 1 mL of 26wt% ammonia water is added to the dilute ethanol solution, and stirred at 300 rpm to form a colorless transparent solution A;

[0011] (3) 0.5 g of dopamine hydrochloride is dissolved in deionized water to form a 0.26 mol / L dopamine solution, which is then added to the A solution, and the stirring is continued at 500 rpm for 24 h to form a brown suspension B;

[0012] (4) The suspension B obtained in step (3) is suction filtered and the precipitate is washed with anhydrous ethanol and water, and then the precipitate is placed in an 80℃ oven for drying for 12 h to obtain polydopamine microspheres PDA;

[0013] (5) 0.4 g of polydopamine microspheres PDA is added to anhydrous ethanol to form a 50 g / L polydopamine sphere dispersion liquid by ultrasonic treatment at a power of 320 W for 10 min;

[0014] (6) 0.1-3.2 mL of tetrabutyl titanate was added to the dispersion of polydopamine spheres, and stirred at 500 rpm for 20 min to form a suspension C;

[0015] (7) The suspension C was added to 76 mL of anhydrous ethanol and stirred uniformly, and 4 mL of deionized water was added dropwise at a speed of 1 mL / s every 30 s, and stirred at 500 rpm for 60 min to form a gray-white suspension D;

[0016] (8) The suspension D obtained in step (7) was separated by suction filtration, and the precipitate obtained by filtration was washed with anhydrous ethanol and water, and the precipitate was dried in an oven at 80°C for 6 h to obtain gray-white core-shell structured titanium dioxide microspheres PDA@TiO2;

[0017] (9) 0.4 g of titanium dioxide microspheres PDA@TiO2 was placed in a muffle furnace and calcined at high temperature in air, and then a large amount of nitrogen and carbon-containing gas released by pyrolysis of the PDA core unstable at high temperature in air was chemically vapor deposited on the titanium dioxide shell to form nitrogen and carbon co-doped titanium dioxide hollow microspheres, and the muffle furnace was heated in a gradient heating mode, heated to 200°C at a rate of 2°C / min, and kept for 1 h, then heated to 450°C at a rate of 2°C / min, and kept for 2 h.

[0018] The ultrasonic power in step (5) is 320 W.

[0019] The washing steps in steps (4) and (8) are: using deionized water to wash the collected product, filtering to obtain the washed product, using deionized water to wash the product again, filtering, and finally uniformly dispersing the filtered product in anhydrous ethanol, filtering again to obtain the final product.

[0020] The volume of tetrabutyl titanate added to the polydopamine sphere dispersion in step (6) is 0.2 mL.

[0021] The PDA core in the titanium dioxide microspheres PDA@TiO2 in step (8) provides a hollow template for the nitrogen and carbon co-doped titanium dioxide hollow microspheres, and provides a nitrogen source and a carbon source at the same time, by fixing the addition amount of PDA sphere core at 0.4 g, changing the addition amount of titanium source tetrabutyl titanate in the titanium dioxide shell to 0.1-3.2 mL to control the nitrogen and carbon doping amounts to be 0.19-0.52 at% and 22.56-28.67 at% respectively, and appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microspheres.

[0022] The application of the polydopamine-mediated nitrogen and carbon co-doped titanium dioxide hollow microspheres in photocatalytic degradation of flowing acetaldehyde gas.

[0023] Compared with the prior art, the present application has the following excellent effects:

[0024] (1) By controlling the content of tetrabutyl titanate, the best polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres are prepared, and the obtained nanospheres have the characteristics of ultra-thin shell, average thickness not greater than 13 nm, uniform thickness, rich porosity, and maximum nitrogen-carbon co-doping amount.

[0025] (2) The preparation process is simple, the cost is low, and the environment is friendly, and most importantly, the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared have very good visible light-driven photocatalytic activity when used for photocatalytic degradation of flowing gaseous acetaldehyde, and the removal rate of the flowing gaseous acetaldehyde under visible light is as high as 90%. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 X-ray diffraction pattern of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1-6 and the comparative example.

[0027] Figure 2 Scanning electron microscope picture of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres H-NT-0.2 prepared for Example 2, and the inserted picture is a transmission electron microscope photo.

[0028] Figure 3 Energy spectrum diagram of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres H-NT-0.2 prepared for Example 2.

[0029] Figure 4 X-ray photoelectron spectroscopy diagram of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1, 2 and 6.

[0030] Figure 5 Nitrogen adsorption desorption analysis diagram of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1-4, Example 6 and the comparative example.

[0031] Figure 6 Pore size distribution curve of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1-4 and Example 6.

[0032] Figure 7 Electron paramagnetic resonance spectroscopy diagram of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1, 2 and 6.

[0033] Figure 8 Dynamic adsorption curve of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1-6 and the comparative example.

[0034] Figure 9The visible light photocatalytic degradation efficiency curve of flowing gaseous acetaldehyde of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres prepared for Examples 1-6 and the comparative example is prepared. DETAILED DESCRIPTION

[0035] For the purpose of describing the present application, the technical solutions and advantages are clearer and more apparent, the present application is further described in detail below in combination with the examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. Those skilled in the art can modify or replace equivalently on the basis of understanding the technical solutions of the present application, without departing from the spirit and scope of the technical solutions of the present application, which should be covered within the protection scope of the present application.

[0036] The raw materials used in the following specific examples are purchased from the market.

[0037] Example 1

[0038] This example is an example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres described in the present application, and the specific steps are as follows:

[0039] (1) 40 mL of anhydrous ethanol was dissolved in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L;

[0040] (2) 1 mL of 26wt% ammonia water was added to the dilute ethanol solution, and stirred at 300 rpm to form a colorless transparent solution A;

[0041] (3) 0.5 g of dopamine hydrochloride was dissolved in deionized water to form a dopamine solution with a concentration of 0.26 mol / L, and then added to solution A, and continued to be stirred at 500 rpm for 24 h to form a brown suspension B;

[0042] (4) The suspension B obtained in step (3) was suction filtered and the precipitate was washed with anhydrous ethanol and water, and then the precipitate was placed in an oven at 80°C for drying for 12 h to obtain polydopamine microspheres PDA;

[0043] (5) 0.4 g of polydopamine microspheres PDA was added to anhydrous ethanol to form a polydopamine ball dispersion solution with a concentration of 50 g / L by ultrasonic treatment at a power of 320 W for 10 min;

[0044] (6) 0.1 mL of tetrabutyl titanate was added to the polydopamine ball dispersion solution, and stirred at a stirring speed of 500 rpm for 20 min to form a suspension C;

[0045] (7) The suspension C was added to 76 mL of anhydrous ethanol and stirred uniformly, and then deionized water was added dropwise at a speed of 1 mL / s for a total of 4 mL every 30 s, and stirred at 500 rpm for 60 min to form a gray-white suspension D;

[0046] (8) The suspension D obtained in step (7) is separated by suction filtration, and the precipitate obtained is washed with anhydrous ethanol and water. The precipitate is placed in an oven at 80℃ and dried for 6h to obtain the gray-white titanium dioxide microspheres PDA@TiO2-0.1, which is abbreviated as PDA@TiO2-0.1, and the same applies below. The PDA core in the titanium dioxide microspheres PDA@TiO2-0.1 provides a hollow template agent for the nitrogen-carbon co-doped titanium dioxide hollow microspheres and provides a nitrogen source and a carbon source. By fixing the PDA ball core addition amount to 0.4g and changing the titanium source tetrabutyl titanate addition amount of the titanium dioxide shell to 0.1mL, the nitrogen and carbon doping amounts are adjusted to 0.52at% and 27.88at% respectively. Appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is conducive to improving the visible light catalytic activity of the titanium dioxide hollow microspheres;

[0047] (9) 0.4g of PDA@TiO2-0.1 is placed in a muffle furnace and calcined at high temperature in air. A large amount of nitrogen and carbon-containing gas released by pyrolysis of the air-unstable PDA core in the high temperature forms a nitrogen-carbon co-doped titanium dioxide hollow microsphere on the titanium dioxide shell by chemical vapor deposition. The label is H-NT-0.1. The heating of the muffle furnace is in a gradient heating mode. The temperature is increased to 200℃ at a rate of 2℃ / min and maintained for 1h. Then the temperature is increased to 450℃ at a rate of 2℃ / min and maintained for 2h.

[0048] Example 2

[0049] This example is another example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to the present application, and the specific steps are as follows:

[0050] (1) 40mL of anhydrous ethanol is dissolved in 90mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28mol / L;

[0051] (2) 1mL of 26wt% ammonia water is added to the dilute ethanol solution and stirred at 300rpm to form a colorless transparent solution A;

[0052] (3) 0.5g of dopamine hydrochloride is dissolved in deionized water to form a dopamine solution with a concentration of 0.26mol / L, which is then added to solution A. Continue stirring at 500rpm for 24h to form a brown suspension B;

[0053] (4) The suspension B obtained in step (3) is suction filtered and the precipitate is washed with anhydrous ethanol and water. The precipitate is placed in an oven at 80℃ and dried for 12h to obtain polydopamine microspheres PDA;

[0054] (5) 0.4 g of polydopamine microspheres PDA was added to anhydrous ethanol to form a 50 g / L polydopamine ball dispersion solution by ultrasonic treatment at a power of 320 W for 10 min;

[0055] (6) 0.2 mL of tetrabutyl titanate was added to the polydopamine ball dispersion solution, and stirred at a stirring speed of 500 rpm for 20 min to form a suspension C;

[0056] (7) The suspension C was added to 76 mL of anhydrous ethanol and stirred uniformly, and deionized water was added dropwise at a speed of 1 mL / s for a total of 4 mL every 30 s, and stirred at 500 rpm for 60 min to form a gray-white suspension D;

[0057] (8) The suspension D obtained in step (7) was separated by suction filtration, and the precipitate obtained by filtration was washed with anhydrous ethanol and water. The precipitate was dried in an oven at 80°C for 6 h to obtain gray-white titanium dioxide microspheres PDA@TiO2-0.2, which is abbreviated as PDA@TiO2-0.2, and the same below. The PDA core in the titanium dioxide microspheres PDA@TiO2-0.2 provides a hollow template for the nitrogen-carbon co-doped titanium dioxide hollow microspheres, and provides a nitrogen source and a carbon source. By fixing the PDA ball core addition amount to 0.4 g, and changing the titanium source tetrabutyl titanate addition amount to 0.2 mL, the nitrogen and carbon doping amounts are adjusted to 0.46 at% and 28.67 at%, respectively. Appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microspheres;

[0058] (9) 0.4 g of PDA@TiO2-0.2 was placed in a muffle furnace and calcined at high temperature in air. After that, a large amount of nitrogen and carbon-containing gas released by pyrolysis of the unstable PDA core at high temperature in air was chemically vapor deposited on the titanium dioxide shell to form nitrogen-carbon co-doped titanium dioxide hollow microspheres, which are marked as H-NT-0.2. The heating of the muffle furnace is in a gradient heating mode, heated to 200°C at a rate of 2°C / min, and kept for 1 h, and then heated to 450°C at a rate of 2°C / min, and kept for 2 h.

[0059] Example 3

[0060] This example is another example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to the present application, and the specific steps are as follows:

[0061] (1) 40 mL of anhydrous ethanol was dissolved in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L;

[0062] (2) 1 mL of 26wt% ammonia water was added to the dilute ethanol solution, and stirred at 300 rpm to form a colorless transparent solution A;

[0063] (3) 0.5 g of dopamine hydrochloride was dissolved in deionized water to form a dopamine solution of 0.26 mol / L, and then added to the solution A, and stirring was continued at 500 rpm for 24 h to form a brown suspension B;

[0064] (4) The suspension B obtained in step (3) was suction filtered and the precipitate was washed with anhydrous ethanol and water, and then the precipitate was dried in an oven at 80°C for 12 h to obtain polydopamine microspheres PDA;

[0065] (5) 0.4 g of polydopamine microspheres PDA was added to anhydrous ethanol, and ultrasonic treatment was performed at a power of 320 W for 10 min to form a polydopamine sphere dispersion solution of 50 g / L;

[0066] (6) 0.4 mL of tetrabutyl titanate was added to the polydopamine sphere dispersion solution, and stirring was performed at a stirring speed of 500 rpm for 20 min to form a suspension C;

[0067] (7) The suspension C was added to 76 mL of anhydrous ethanol and stirred uniformly, and deionized water was added dropwise at a speed of 1 mL / s every 30 s for a total of 4 mL, and stirring was performed at 500 rpm for 60 min to form a gray-white suspension D;

[0068] (8) The suspension D obtained in step (7) was suction filtered and separated, the precipitate obtained by filtration was washed with anhydrous ethanol and water, and then the precipitate was dried in an oven at 80°C for 6 h to obtain gray-white titanium dioxide microspheres PDA@TiO2-0.4, which is abbreviated as PDA@TiO2-0.4, and the same below. The PDA core in the titanium dioxide microspheres PDA@TiO2-0.4 provides a hollow template agent for the nitrogen-carbon co-doped titanium dioxide hollow microspheres and provides a nitrogen source and a carbon source, and by fixing the PDA sphere core addition amount to 0.4 g and changing the titanium source tetrabutyl titanate addition amount of the titanium dioxide shell to 0.4 mL, the nitrogen and carbon doping amounts can be adjusted, and appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microspheres;

[0069] (9) 0.4 g of PDA@TiO2-0.4 was placed in a muffle furnace and calcined at high temperature in air, and then a large amount of nitrogen and carbon-containing gas released by pyrolysis of the air-unstable PDA core at high temperature in air was chemically vapor deposited on the titanium dioxide shell to form nitrogen-carbon co-doped titanium dioxide hollow microspheres, which are marked as H-NT-0.4. The heating of the muffle furnace is in a gradient heating mode, heated to 200°C at a rate of 2°C / min, kept for 1 h, and then heated to 450°C at a rate of 2°C / min, kept for 2 h.

[0070] Example 4

[0071] This embodiment is another example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to the present application, and the specific steps are as follows:

[0072] (1) Dissolve 40 mL of anhydrous ethanol in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L;

[0073] (2) Take 1 mL of 26wt% ammonia water and add it to the dilute ethanol solution, stir and disperse at 300 rpm to form a colorless transparent solution A;

[0074] (3) Dissolve 0.5 g of dopamine hydrochloride in deionized water to form a 0.26 mol / L dopamine solution, then add it to solution A, and continue to stir at 500 rpm for 24 h to form a brown suspension B;

[0075] (4) Filter the suspension B obtained in step (3) and wash the precipitate with anhydrous ethanol and water, then place the precipitate in an 80°C oven and dry for 12 h to obtain polydopamine microspheres PDA;

[0076] (5) Take 0.4 g of polydopamine microspheres PDA and add it to anhydrous ethanol to form a 50 g / L polydopamine ball dispersion solution under ultrasonic power of 320 W for 10 min;

[0077] (6) Add 1.0 mL of tetrabutyl titanate to the polydopamine ball dispersion solution, and stir at a stirring speed of 500 rpm for 20 min to form a suspension C;

[0078] (7) Add the suspension C to 76 mL of anhydrous ethanol and stir evenly, then add 4 mL of deionized water dropwise at a speed of 1 mL / s every 30 s, and stir at 500 rpm for 60 min to form a gray-white suspension D;

[0079] (8) Filter the suspension D obtained in step (7) and separate, wash the precipitate obtained by filtration with anhydrous ethanol and water, then place the precipitate in an 80°C oven and dry for 6 h to obtain gray-white core-shell structure titanium dioxide microspheres PDA@TiO2-1.0, which is referred to as PDA@TiO2-1.0 hereinafter. The PDA core in the titanium dioxide microspheres PDA@TiO2-1.0 provides a hollow template for the nitrogen-carbon co-doped titanium dioxide hollow microspheres, and also provides a nitrogen source and a carbon source. By fixing the PDA ball core addition amount to 0.4 g and changing the titanium source tetrabutyl titanate addition amount to 1.0 mL, the nitrogen and carbon doping amounts can be adjusted. Appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microspheres;

[0080] (9) 0.4 g of PDA@TiO2-1.0 was placed in a muffle furnace for high-temperature calcination in air, after which a large amount of nitrogen and carbon-containing gas released by pyrolysis of the air-unstable PDA core in the titanium dioxide shell was subjected to chemical vapor deposition to form nitrogen-carbon co-doped titanium dioxide hollow microspheres, marked as H-NT-1.0, and the muffle furnace was heated in a gradient heating mode, heated to 200°C at a rate of 2°C / min, kept for 1 h, and then heated to 450°C at a rate of 2°C / min, kept for 2 h.

[0081] Example 5

[0082] This example is the fifth example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres described in the present application, and the specific steps are as follows:

[0083] (1) 40 mL of anhydrous ethanol was dissolved in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L;

[0084] (2) 1 mL of 26wt% ammonia water was taken and added to the dilute ethanol solution, and stirred at 300 rpm to form a colorless transparent solution A;

[0085] (3) 0.5 g of dopamine hydrochloride was dissolved in deionized water to form a 0.26 mol / L dopamine solution, which was then added to solution A, and stirring was continued at 500 rpm for 24 h to form a brown suspension B;

[0086] (4) The suspension B obtained in step (3) was suction filtered and the precipitate was washed with anhydrous ethanol and water, and the precipitate was placed in an 80°C oven and dried for 12 h to obtain polydopamine microspheres PDA;

[0087] (5) 0.4 g of polydopamine microspheres PDA was taken and added to anhydrous ethanol to form a 50 g / L polydopamine sphere dispersion solution under ultrasonic power of 320 W for 10 min;

[0088] (6) 1.6 mL of tetrabutyl titanate was added to the polydopamine sphere dispersion solution, and stirred at a stirring speed of 500 rpm for 20 min to form a suspension C;

[0089] (7) The suspension C was added to 76 mL of anhydrous ethanol and stirred uniformly, and deionized water was added dropwise at a rate of 1 mL / s every 30 s for a total of 4 mL, and stirred at 500 rpm for 60 min to form a gray-white suspension D;

[0090] (8) The suspension D obtained in step (7) is separated by suction filtration, and the precipitate obtained is washed with anhydrous ethanol and water. The precipitate is placed in an oven at 80°C and dried for 6h to obtain the gray-white core-shell structured titanium dioxide microspheres PDA@TiO2-1.6, which is abbreviated as PDA@TiO2-1.6, and the same below. The PDA core in the titanium dioxide microspheres PDA@TiO2-1.6 provides a hollow template agent for the nitrogen-carbon co-doped titanium dioxide hollow microspheres and provides a nitrogen source and a carbon source. By fixing the PDA ball core addition amount to 0.4g and changing the titanium source tetrabutyl titanate addition amount of the titanium dioxide shell to 1.6mL, the nitrogen and carbon doping amount is adjusted. Appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microspheres;

[0091] (9) 0.4g of PDA@TiO2-1.6 is placed in a muffle furnace and calcined at high temperature in air. A large amount of nitrogen and carbon-containing gas released by pyrolysis of the air-unstable PDA core at high temperature in air is chemically vapor deposited on the titanium dioxide shell to form nitrogen-carbon co-doped titanium dioxide hollow microspheres, which are marked as H-NT-1.6. The muffle furnace heating is in a gradient heating mode, heated to 200°C at a rate of 2°C / min, kept for 1h, and then heated to 450°C at a rate of 2°C / min, kept for 2h.

[0092] Example 6

[0093] This example is the sixth example of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to the present application, and the specific steps are as follows:

[0094] (1) 40mL of anhydrous ethanol is dissolved in 90mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28mol / L;

[0095] (2) 1mL of 26wt% ammonia water is added to the dilute ethanol solution, and stirred at 300rpm to form a colorless transparent solution A;

[0096] (3) 0.5g of dopamine hydrochloride is dissolved in deionized water to form a dopamine solution with a concentration of 0.26mol / L, and then added to the A solution. Continue to stir at 500rpm for 24h to form a brown suspension B;

[0097] (4) The suspension B obtained in step (3) is suction filtered and the precipitate is washed with anhydrous ethanol and water. The precipitate is placed in an oven at 80°C and dried for 12h to obtain polydopamine microspheres PDA;

[0098] (5) 0.4g of polydopamine microspheres PDA is added to anhydrous ethanol to form a 50g / L polydopamine ball dispersion solution by ultrasonic treatment at a power of 320W for 10min;

[0099] (6) 3.2 mL of tetrabutyl titanate was added into the dispersion of polydopamine spheres, and stirred at 500 rpm for 20 min to form a suspension C;

[0100] (7) The suspension C was added into 76 mL of anhydrous ethanol and stirred uniformly, and 4 mL of deionized water was added dropwise at a speed of 1 mL / s every 30 s, and stirred at 500 rpm for 60 min to form a grayish white suspension D;

[0101] (8) The suspension D obtained in step (7) was separated by suction filtration, and the precipitate obtained by filtration was washed with anhydrous ethanol and water, and the precipitate was placed in an oven at 80°C and dried for 6 h to obtain a grayish white core-shell structured titanium dioxide microsphere PDA@TiO2-3.2, which is abbreviated as PDA@TiO2-3.2, and the same below. The PDA core in the titanium dioxide microsphere PDA@TiO2-3.2 provides a hollow template for the nitrogen-carbon co-doped titanium dioxide hollow microsphere and provides a nitrogen source and a carbon source. By fixing the PDA sphere core addition amount to 0.4 g and changing the titanium source tetrabutyl titanate addition amount of the titanium dioxide shell to 3.2 mL, the nitrogen and carbon doping amounts are adjusted to 0.19 at% and 22.56 at%, respectively. Appropriate nitrogen and carbon doping can promote the formation of titanium dioxide surface defects such as oxygen vacancies, which is beneficial to improve the visible light catalytic activity of the titanium dioxide hollow microsphere;

[0102] (9) 0.4 g of PDA@TiO2-3.2 was placed in a muffle furnace and calcined at high temperature in air. After that, a large amount of nitrogen and carbon-containing gas released by pyrolysis of the air-unstable PDA core in the air at high temperature was chemically vapor deposited on the titanium dioxide shell to form a nitrogen-carbon co-doped titanium dioxide hollow microsphere, which is marked as H-NT-3.2. The heating of the muffle furnace is in a gradient heating mode, heated to 200°C at a rate of 2°C / min, and kept for 1 h, and then heated to 450°C at a rate of 2°C / min, and kept for 2 h.

[0103] Comparative Example

[0104] The comparative example is a blank control group of the preparation method of the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microsphere according to the present application. According to the preparation process of Examples 1-6, the difference is that the polydopamine microsphere is not added in step (5) of the comparative example, and the volume of tetrabutyl titanate added in step (6) is 0.2 mL. A titanium dioxide sample is prepared, which is marked as T. Table 1 is the test results of Examples 1-6 and the comparative example.

[0105] Table 1 Results of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres obtained under different test conditions

[0106]

[0107]

[0108] From the test results of Table 1, it can be seen that the comparative titanium dioxide (T) has a photocatalytic efficiency of 49% for acetaldehyde under visible light. In Examples 1-6, the shell thickness of the different polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microsphere samples prepared by synthesis increases with the increase of the amount of tetrabutyl titanate added, and the overall photocatalytic degradation efficiency appears to increase first and then decrease. In Examples 1-4 and Example 6, the BET specific surface area, average pore size, and mesopore volume all decrease with the increase of the shell thickness, and the BET specific surface area, average pore size, and mesopore volume of Examples 1 and 2 are much higher than those of the other examples, and the increase of the shell thickness has a negative impact on the pore structure. The polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres (H-NT-0.2) prepared under the condition of 0.2 mL of tetrabutyl titanate added have an average shell thickness of 13 nm, and have the best performance for visible light-driven catalytic degradation of gaseous flowing acetaldehyde, and the removal efficiency of gaseous flowing acetaldehyde under visible light driving is as high as 90%, which is much higher than that of the comparative titanium dioxide.

[0109] Table 2 Element Proportion Table of Some Polydopamine-Mediated Nitrogen-Carbon Co-Doped Titanium Dioxide Hollow Microspheres

[0110]

[0111] From the results of Table 2, it can be seen that in Examples 1, 2, and 6, the different polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microsphere samples prepared by synthesis successfully doped nitrogen and carbon elements, and the sum of the proportions of nitrogen and carbon elements in Examples 1 and 2 is much larger than that in Example 6. The sum of the proportions of nitrogen and carbon elements in the polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres (H-NT-0.2) prepared under the condition of 0.2 mL of tetrabutyl titanate added is the largest, which may be because the thinner and more complete hollow titanium dioxide shell structure of H-NT-0.2 is conducive to nitrogen and carbon doping.

Claims

1. An application of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres in the photocatalytic degradation of dynamic acetaldehyde gas, characterized in that, A method for preparing polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres includes the following steps: (1) Dissolve 40 mL of anhydrous ethanol in 90 mL of deionized water to prepare a dilute ethanol solution with a concentration of 5.28 mol / L; (2) Take 1 mL of ammonia water with a mass fraction of 26 wt% and add it to the dilute ethanol solution. Stir and disperse at 300 rpm to form a colorless and transparent solution A. (3) Dissolve 0.5 g of dopamine hydrochloride in deionized water to form a 0.26 mol / L dopamine solution, then add it to solution A and continue stirring at 500 rpm for 24 h to form a brown suspension B; (4) The suspension B obtained in step (3) was filtered and the precipitate was washed with anhydrous ethanol and water. The precipitate was dried in an oven at 80 °C for 12 h to obtain polydopamine microspheres PDA. (5) Take 0.4 g of polydopamine microspheres (PDA) and add them to anhydrous ethanol. Sonicate at 320 W for 10 min to form a 50 g / L polydopamine microsphere dispersion. (6) Add 0.2 mL of tetrabutyl titanate to the polydopamine sphere dispersion and stir at 500 rpm for 20 min to form suspension C; (7) Add suspension C to 76 mL of anhydrous ethanol and stir until homogeneous. Add 4 mL of deionized water dropwise at a rate of 1 mL / s every 30 s. Stir at 500 rpm for 60 min to form grayish-white suspension D. (8) The suspension D obtained in step (7) was separated by filtration. The precipitate obtained by filtration was washed with anhydrous ethanol and water. The precipitate was dried in an oven at 80 ℃ for 6 h to obtain grayish-white core-shell structured titanium dioxide microspheres PDA@TiO2. The PDA core in the titanium dioxide microspheres PDA@TiO2 provides a hollow template agent for the nitrogen-carbon co-doped titanium dioxide hollow microspheres, while also providing nitrogen and carbon sources. Appropriate nitrogen and carbon doping promotes the formation of oxygen vacancies on the surface of titanium dioxide, which is beneficial to improving the visible light photocatalytic activity of the titanium dioxide hollow microspheres. (9) 0.4 g of titanium dioxide microspheres PDA@TiO2 were placed in a muffle furnace and calcined at high temperature in air. Then, a large amount of nitrogen and carbon-containing gas was released by the nuclear thermal decomposition of the PDA at high temperature in air and chemical vapor deposition was carried out on the titanium dioxide shell to form nitrogen-carbon co-doped hollow titanium dioxide microspheres. The muffle furnace heating was in gradient heating mode, heated to 200 °C at a rate of 2 °C / min and held for 1 h, and then heated to 450 °C at a rate of 2 °C / min and held for 2 h.

2. The application of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to claim 1 in the photocatalytic degradation of dynamic acetaldehyde gas, characterized in that, The ultrasonic power in step (5) is 320 W.

3. The application of polydopamine-mediated nitrogen-carbon co-doped titanium dioxide hollow microspheres according to claim 1 in the photocatalytic degradation of dynamic acetaldehyde gas, characterized in that, The washing steps described in steps (4) and (8) are as follows: wash the collected product with deionized water, filter to obtain the washed product, wash the product with deionized water again, filter, and finally evenly disperse the filtered product in anhydrous ethanol, filter again, and obtain the final product.

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